Spectral Studies and Bactericidal, Fungicidal, Insecticidal andParasitological Activities of Organotin(IV) Complexes of ThioSchiff Bases Having no Donor Atoms

Abstract

Twelve new organotin(IV) complexes of the type RnSnLm [where n = 3, m = 1, R = CH3 or C6H5; n = 2, m = 2, R = C6H5 or C4H9 ; L = anion of Schiff bases derived from the condensation of 2-amino-5-(o-anisyl)-l,3,4-thiadiazole with salicylaldehyde (HL-1), 2- hydroxynaphthaldehyde (HL-2) and 2-hydroxyacetophenone (HL-3)] have been synthesized and characterized by elemental analysis, molar conductances, electronic, infrared, far-infrared, 1H NMR and 119Sn Mössbauer spectral studies. Thermal studies of two complexes, viz., Ph3Sn (L-1) and Ph2Sn(L-2)2 have been carried out in the temperature range 25-1000∘C using TG, DTG and DTA techniques. All these complexes decompose gradually with the formation of SnO2 as an end product. In vitro antimicrobial activity of the Schiff bases and their complexes has also been determined against Streptococcus faecalis, Klebsiella pneumoniae, Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus Penicillin resistance (2500 units), Candida albicans, Cryptococcus neoformans, Sporotrichum schenckii, Trichophyton mentagrophytes and Aspergillus fumigatus. The Schiff bases (HL-1), (HL-2) and the organotin(IV) compounds have also been tested against various important herbicidal, fungicidal, insecticidal species and also for parasitological activity against freeliving nematode.

Synthesis, structural characterization, biological activity and thermal study of tri‐ and diorganotin(IV) complexes of Schiff base derived from 2‐aminomethylbenzimidazole

“…3. The ν(Sn-O) band in the region 527-574 cm −1 [20,26] is also observed in the spectra of all of the synthesized complexes. …”

“…Absence of ν(OH) mode in all of the studied complexes suggests the deprotonation of phenolic -OH of Hsal-ambmz and its subsequent coordination through the oxygen atom. [16,19,20,22,23] Two strong bands around 1530 ± 10 and 1313 ± 6 cm −1 in the complexes were observed at lower wave numbers as compared with uncoordinated Hsal-ambmz (1561 and 1320 cm −1 ), indicating the participation of phenolic oxygen in bonding with tin. [20] Further, the IR spectrum of Hsal-ambmz showed a very sharp and strong band due to the ν(-C N-) of azomethine at 1638 cm −1 .…”

“…Since the imidazole ring has an aromatic character, a shoulder at 1615 cm −1 may be assigned to ν(C N) of the imidazole ring. [16,19,20,22,24] In the IR spectra of the studied complexes, a single sharp band at 1621 ± 8 cm −1 was observed because the azomethine ν(C N) merges with ν(C N) of imidazole ring, indicating the coordination of azomethine nitrogen to tin. Moreover, the presence of two medium intensity bands in the regions 3052-3064 and 2954-3044 cm −1 in Hsal-ambmz as well as in most of the complexes indicates that the N-H of imidazole ring does not participate in the coordination.…”

“…Moreover, there were a few sharp bands observed in the region 240-270 nm in the spectra of complexes, which could be assigned to charge transfer bands. [16,18 -21] It has been reported [16,20] that a metal/metalloid is capable of forming dπ -pπ bonds with ligands containing nitrogen as donor atom. The tin atom has its 5d orbitals completely vacant and hence L → M bonding can take place by the acceptance of pair of electron from nitrogen or oxygen donor atom of the ligands.…”

“…oxygen and nitrogen in (sal-ambmz) −1 , are not in axial positions, as one would expect from the steric properties of the bidentate ligand. [16,20] Hence the triorganotin(IV) chelates of monofunctional bidentate Schiff base (HL) with ON donor site exhibit trigonal-bipyramidal geometry with either fac or mer configuration (Fig. 2).…”